1. Field of the Invention
The present invention relates to a gas supply path structure and a gas supply method adapted in such a way that a fluid path is formed for a compressible fluid (mainly, compressible gas) to flow into or out of the path and that the fluid is ejected from a predetermined portion midway of the fluid path and, particularly, this gas supply path structure is suitably applicable to a laser oscillating apparatus using it for supply of a laser gas, an exposure apparatus having the laser oscillating apparatus as a component, and a device production method therewith.
2. Related Background Art
In recent years so-called excimer lasers are drawing attention as high output lasers only which can be oscillated in the ultraviolet region, and they are expected to be applied in the electronics industries, chemical industries, energy industries, etc., specifically, to processing, chemical reaction, etc. of metal, resin, glass, ceramics, semiconductors, and so on.
The functional principles of excimer laser oscillating apparatus will be described. First, a laser gas of Ar, Kr, Ne, F2, He, Xe, Cl2, or the like filled in a laser tube is brought into an excited state by electron beam irradiation, discharge, or the like. In the case of the KrF excimer laser, for example, the excited F atoms are coupled with inactive Kr atoms being in the ground state to create KrF, which is molecules existing only in the excited state. These molecules are called excimers. The excimers are instable and soon emit ultraviolet light to fall into the ground state. This phenomenon is called spontaneous emission and the excimer laser oscillating apparatus is one making use thereof so as to amplify the emitted light into phase-aligned light in an optical resonator composed of a pair of reflectors and take it out in the form of a laser beam.
The excimer laser oscillating apparatus is becoming the mainstream of light sources used in various modern industries on one hand and has the problem of extremely short light emission time due to exhaustion of the laser gas with light emission on the other hand. Namely, particularly in the case of the KrF laser, the ArF laser, and the F2 laser among the excimer lasers, it is not easy to maintain the light emission over a long time, because a relatively long time is necessary for return from the state of light emission of the excited molecules to the original state of F2 molecules.
In order to extend the light emission time by replenishment with the laser gas, it is necessary to always supply the laser gas at high speed. Generation of gas flow at high speed, however, can result in forming a shock wave, which could cause incapability of functioning as a laser oscillating apparatus; specifically, it could cause an offset of the optical axis of laser, loosening of joints for the laser gas, breakage of ceramics, metal fatigue, and so on. For example, when exposure or the like is carried out, vibration caused by the shock wave will be fatal disturbance rather than the above.